Continuous analyte monitoring systems, such as continuous glucose monitoring systems, use analyte sensors, a portion of which is placed in contact with the patient's bodily fluid such as interstitial fluid or blood. The analyte sensor such as glucose sensors are configured with electrodes such as a working electrode, a counter electrode and a reference electrode, and where at least a portion of the sensor is placed in vivo so as to detect the level of the patient's analyte. In the three electrode configuration, the reference electrode is maintained substantially current free, and is configured to establish a substantially constant electrical potential difference with respect to the working electrode. The electrical potential difference then is used to drive certain electrochemical reactions that result in a current signal which is directly proportional to the level of analyte in the patient (such as the patient's glucose concentration).
The analyte sensor configuration described above, and in most glucose sensors that employ multiple electrodes for detecting the glucose level, for example, the counter electrode is generally configured to close the circuit. That is, since the electrons resulting from the electrochemical reactions by the analyte sensor are flowing into the working electrode from the electrolyte solution (the patient's body), the counter electrode of the analyte sensor needs to dispose of the electrons back into the electrolyte (that is, the counter electrode must find molecules or ions that can be reduced). The applied electrical potential at the counter electrode is regulated through a feedback loop such that the necessary reduction reactions can take place. Therefore, it is necessary for the counter electrode of the analyte sensor to be electrically coupled to the human body.
In view of the foregoing, it would be desirable to have methods and device for providing a compact, cost effective analyte sensor configuration. Indeed, it would be desirable to have methods and device for providing analyte sensors with external counter electrode which is not placed in vivo along with the working and reference electrodes of the analyte sensor so as to be in fluid contact with the patient's analyte. Moreover, it would be desirable to have method and system for manufacturing analyte sensors to achieve cost effectiveness and scalability by, for example, reducing the number of necessary manufacturing steps.